1. Field of the Invention
This invention generally relates to duplex electrical grounding receptacles and, more particularly, to a one-piece multi-function grounding strip assembled within the receptacle.
2. Description of Related Art
A conventional grounded duplex electrical receptacle has a pair of electrical outlets, each having two power sockets for receiving two power prongs of an electrical plug, and one grounding socket for receiving a grounding prong of the plug. The receptacle is conventionally installed in a wall-mounted electrical junction box to which two power wires and a ground wire are routed from a power supply. Each wire is connected to a respective screw mounted on the receptacle. Each screw is threaded into, and makes electrical contact with, a respective electrically conductive strip located within the receptacle. Thus, a first power strip spans the distance between, and interconnects, associated power sockets of both outlets; a second power strip spans the distance between, and interconnects, other associated power sockets of both outlets; and a grounding strip spans the distance between, and interconnects, associated grounding sockets of both outlets.
A conventional wall plate is mounted over the receptacle. The wall plate, which can be made of metal or plastic, has openings corresponding to the spacing and size of the electrical outlets so that the outlets remain exposed after the wall plate has been mounted over the receptacle. The exposed outlets enable the three-pronged electrical plugs to be inserted into the corresponding sockets of the outlets.
As previously noted, a grounding screw is threaded into the grounding strip. The ground wire at the junction box is exposed at its end and wrapped at least partly underneath the head of the grounding screw to provide a reliable grounding for the receptacle. The grounding screw is subject to external forces, particularly during wiring of the receptacle, which forces tend to pull the grounding screw from its grounding strip. To prevent such removal, the grounding strip according to the prior art was typically made of a metal having a thickness of at least 0.030 in. and extruded to a 1/16 in. long cylinder in order to provide a minimum of two threads at 32 threads per inch, for engaging the grounding screw. Two threads were considered the minimum necessary to withstand expected removal forces when the screw is torqued down on the wire with a rotational force of 14 in.-lbs.
Although the known grounding strips have been generally satisfactory for their intended purposes, they are undesirable in that the relatively large thickness dimension of the grounding strips contribute to high manufacturing costs. Also, they generally are made up of at least two parts: thick metal for the screw terminal, thin metal for the female, male prong contacts, and some means to reliably fasten the two parts.
Another problem with the known grounding strips is that they typically had to be held in position between upper and lower housing parts of the receptacle during assembly therewith. Experience has shown that the grounding strip would sometimes be shifted in position, thereby misaligning the strip and complicating the overall assembly procedure.